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Ultrashort lasers that generate laser pulses down to picosecond and femtosecond range have advanced over the past decade from delicate lab systems to robust industry machines. The availability of stable ultrashort laser systems opens up a wide range of exciting applications from transparent material processing such as waveguide fabrication to bio applications such as cell ablation. The fundamental aspects of ultrashort pulse material interaction are still remaining an active research topic. Here, we focus on the investigation of how ultrashort pulses, particularly picosecond laser pulses, interact with the bulk of transparent materials such as borosilicate glass, fused silica and sapphire. We investigate damage inside the bulk of borosilicate glass, fused silica, and sapphire by a single shot of IR picosecond laser pulse experimentally. In our experiments, extended bulk damage tracks with an aspect ratio of about 1:10 are generated. The damage morphology in each of the material is found to be different. We also numerically model pulse propagation and electron dynamics in borosilicate glass and fused silica in both picosecond and femtosecond regimes. The shape and size of the damage sites are shown to correspond to an electron cloud with density of about 10^20 cm^-3. The underlying mechanism of electron generation by multiphoton ionization and avalanche ionization is numerically investigated. The multiphoton ionization rate and avalanche ionization rate are determined by fitting experimental results. The relative role of multiphoton ionization and avalanche ionization are numerically studied and the percentage of electron contribution from each ionization channels are investigated.

A pure Ce-doped silica fiber is fabricated using modified chemical vapor deposition (MCVD) technique. Fluorescence characteristics of a Ce-doped silica fiber are experimentally investigated with continuous wave pumping from 440 nm to 405 nm. Best pump absorption and broad fluorescence spectrum is observed for ~ 405 nm laser. Next, the detailed analysis of spectral response as a function of pump power and fiber length is performed. It is observed that a -10dB spectral width of ~ 280 mn can be easily achieved with different combinations of the fiber length and pump power. Lastly, we present, for the first time to the best of our knowledge, a broadband fluorescence spectrum with -10dB spectral width of 301 nm, spanning from ~ 517.36 nm to ~ 818 nm, from such fibers with non-UV pump lasers.

The editors introduce the focus issue on "Advanced Solid-State Lasers (ASSL) 2015", which is based on the topics presented at a congress of the same name held in Berlin, Germany, from October 4 to October 9, 2015. This focus issue, jointly prepared by Optics Express and Optical Materials Express, includes 23 contributed papers (17 for Optics Express and 6 for Optical Materials Express) selected from the voluntary submissions from attendees who presented at the congress and have extended their work into complete research articles. We hope this focus issue offers a good snapshot of a variety of topical discussions held at the congress and will contribute to the further expansion of the associated research areas., QC 20160405

The editors introduce the focus issue on "Advanced Solid-State Lasers (ASSL) 2014,"which is based on the topics presented at a congress of the same name held in Shanghai, China, from October 27 to November 1, 2014. This Focus issue, jointly prepared by Optics Express and Optical Materials Express, includes 28 contributed papers (21 for Optics Express and 7 for Optical Materials Express) selected from the voluntary submissions by attendees who presented at the congress and have extended their work into complete research articles. We hope this focus issue offers a useful snapshot of the variety of topical discussions held at the congress and will contribute to the further expansion of the associated research areas., QC 20150506

The editors introduce the focus issue on "Advanced Solid-State Lasers (ASSL) 2013," which is based on the topics presented at a congress of the same name held in Paris, France, from October 27 to November 1, 2013. This focus issue, jointly prepared by Optics Express and Optical Materials Express, includes 21 contributed papers (18 for Optics Express and 3 for Optical Materials Express) selected from the voluntary submissions from attendees who presented at the congress and have extended their work into complete research articles. We hope this focus issue offers a good snapshot of a variety of topical discussions held at the congress and will contribute to the further expansion of the associated research areas., QC 20140613

Telluride glasses possess the widest infrared window of all amorphous materials and are key to a number of long-wavelength applications such as bio-sensing. However they are not intrinsically good glass formers and require significant materials engineering for device fabrication. Strategies for stable glass engineering are presented and the fabrication of far infrared optical fibers is described. A new type of optical sensor based on electrophoretic capture of protein is also presented. This sensor is based on a conducting telluride glass which can act as both a capture electrode and an infrared optical element for collecting vibrational signatures of target molecules such as proteins.

Proceedings of the 16th International Conference, Palazzo dei Congressi Stresa, Italy, June 9--13, 2008, Low jitter 500-fs pulse trains at a fundamental repetition rate of 3.2 GHz, from an Erfiber laser with a saturable Bragg reflector. An increase in repetition rate of femtosecond fiberlasers by one order of magnitude.

The features of the Furnace Chemical Vapor Deposition (FCVD) method of manufacturing preforms for special optical fibers are considered. It is shown that misalignment of substrate silica tube and furnace hole axes has a negative effect on the quality of fabricated preforms, leading to angular and radial asymmetry of the refractive index profile. Ways of getting rid of this and other disadvantages of the FCVD method are described. Some advantages of the FCVD method over the MCVD method are shown. It was demonstrated that the FCVD method, despite some drawbacks, allows to manufacture high-quality fiber preforms with good symmetry of the refractive index profile, and thus it is promising for fabrication of dispersion, dispersion varying and active fibers.

We propose here a liquid level sensor using a long period fiber grating (LPFG) in which direct liquid level measurement is carried out by utilising an LPFG, 100mm in length and a periodicity of 1mm. The LPFG was exposed to liquids with varying levels and the wavelength shift of a selected loss band of the transmission spectra was monitored using a broadband light source and an optical spectrum analyzer. The mechanism of this LPFG sensor is based on the fact that the effective Refractive Index (RI) of a cladding mode is directly dependant on the RI of the surrounding medium, be it air, or in this case water and petrol. As the surrounding RI changes, so does the phase matching condition of the LPFG. The result for the level change of the liquid with a specific RI is both a shift in wavelength and a change in the attenuation level of the selected loss band. For the selected loss band, continuous wavelength shifts of 9.5 nm and 25 nm for 100 mm of water and petrol level change have been observed respectively, with sub-millimetre accuracy.

In this dissertation I report the development of high power pulsed fiber laser systems. These systems utilize phosphate glass fiber for active elements, instead of the industry-standard silica fiber. Because the phosphate glass allows for much higher doping of rare-earth ions than silica fibers, much shorter phosphate fibers can be used to achieve the same gain as longer silica fibers.This single-frequency laser technology was used to develop an all-fiber actively Q-switched fiber lasers. A short cavity is used to create large spacing between longitudinal modes. Using this method, we demonstrated the first all-fiber Q-switched fiber laser in the 1 micron region.In addition to creating high peak powers with Q-switched lasers, created even higher powers using fiber amplifier systems. High power fiber lasers typically produce spectral broadening through the nonlinear effects of stimulated Raman scattering, stimulated Brullion scattering, and self-phase modulation. The thresholds for these nonlinearities scale inversely with intensity and length. Thus, we used a short phosphate fiber gain stage to reduce the length, and a large core fiber final stage to reduce intensity. In this way we were able to generate high peak power pulses while avoiding visible nonlinearities, and keeping a narrow bandwidth.The immediate goal of developing these high power fiber laser systems was to generate narrowband terahertz radiation. Two different wavelengths were combined into the final amplifier stage at orthogonal polarizations. These were collimated and directed into a GaSe crystal, which has a very high figure of merit for THz generation. The two wavelengths combined in the crystal through the process of nonlinear difference frequency generation. This produced a narrowband beam of THz pulses, at higher powers than previous narrowband THz pulses produced by eyesafe fiber lasers.

In this dissertation, the spectroscopic properties of thulium doped tellurite and thulium doped germanate glass are characterized. Absorption and emission spectra, lifetime, Fourier Transform Infrared Spectroscopy (FTIR), and thermo-gravimetric analysis are utilized to characterize the thulium doped tellurite bulk glass samples. Judd-Oflet theory, Fuchtbauer-ladenburg theory, Kushida's model, Burshtein's hopping model, Miyakawa's non-resonant energy transfer model are employed in ab-initio calculation of cross relaxation energy transfer. The fundamental mechanism of cross relaxation energy transfer is examined through ab-initio calculation and self-calibrating spectroscopy.Thulium doped tellurite glass microspheres are fabricated by spin casting technique. Single mode 2-mm laser is demonstrated from tellurite microsphere with high thulium doping concentration. General laser condition for self-terminating transition is discussed and concluded. Demonstration of 1.5-mm laser is achieved from a self-terminating transition of thulium doped in tellurite microsphere through a cooperative lasing technique.Highly efficient 1.9 micron fiber laser is demonstrated in thulium doped germanate fiber laser. The slope efficiency of the fiber laser is 58%, which indicates a quantum efficiency of 1.79. Single frequency laser operation at 1.9 micron has been successfully accomplished. A fiber based Fabry-Perot interferometer is utilized as a scanning filter to examine the single frequency operation. 4 W laser output has been achieved from a 40 cm long Tm-doped germanate double cladding fiber laser.

Long period fiber grating (LPFG) can be used as active gain controlling device in EDFA. However, LPFGs fabricated in the standard telecom fiber only have a typical temperature sensitivity of 3-10nm/100°C, which may not be sufficient for implementing tuneable filters capable of wide tuning range and high tuning efficiency. In this paper, we report a theoretical and experimental investigation of thermal properties of LPFGs fabricated in B/Ge co-doped optical fiber. We have found that the temperature sensitivity of the LPFGs in the B/Ge fiber is considerably increased compared with those produced in the standard fiber. The LPFGs written in the B/Ge fiber have achieved, on average, one order of magnitude higher sensitivity than that of the LPFGs produced in the standard telecom fiber. We have also identified that the thermal response of LPFG is strongly dependent on the order of the coupled resonant cladding mode. The maximum sensitivity of 1.75nm/°C achieved by the 10th cladding mode of the 240μm LPFG is nearly 24 times that of the minimum value (0.075nm/C) exhibited by the 30th mode of the 34μm LPFG. Such devices may lead to high-efficiency and low-cost thermal/electrical tunable loss filters or sensors with extremely high temperature resolution.